Thermal control for air-compressors.



.Patellted J E. HILL. THERMAL CONTROL POR AIR GOMPRESSORS. APPLIOATIQN FILED my 15, V1912. 1,068,432..

i in temperature is still hotter.

pressors capacity or gas compressor when `the return stroke of v EBENEZER HILL, 0]."v NORWALK, CONNECTICUT.

THERMAL CONTROL FOR AIRCOMPRESSORS.

recense.

Specification of Letters Patent.

rammed Jury anims.

Application filed May 15, 1912. Serial No. 697,403.

To all whom t may concern: K

Be it known that I, EBENEZER HILL, a' citizen of the United States, residing at Norwalk, in the county of Fairfield and State of Connecticut, have invented a new and useful Improvement in Thermal Control for Air-Compressors, of which' the following is a specification. v

This invention relates to means designed to exhaust o rrelieve the pressure in an air the heat evolved by the act of compressing the air`or gas raises the temperature above a predetermined d'egree.

In the ordinary operation of an air compressor heat is developed in the air undergoing compression. The amountof this heat depends uponthe number for by the designers of compressors. It oftens happens, however, that a compressor will suddenly apparent cause-therebeing no change in either speed or pressure. Some timesthis heating increases to such an extent as to set the lubricating oil on re, and some times even vaporizing the oil and causing disastrous explosions. Frequently when such heating occurs, after a short period of running warm the discharged air drops to its normal temperature. The cause of this rise that some foreign body gets under an air valve and causes it to leak. When a leak occurs the air which is being compressed, instead of being held by the valve, flows backward through the valve on the piston. On the next forward stroke this air is again forced through the leaking valve while it is still hot, and being again compressed it 'becomes Thus, in proportion to the degree of the leak, the temperature of the dis charged air compressed is increased The larger the leak, the greater the heat. `A leak being constant it is evident that a leakpwhich might'be only a small per centof. a comwhen lit is running atnormal full speed. becomes a very much larger per cent. ofits capacity when the compressor is slowed down to. a few revolutions perminute. v Therefore,'a leak which would be hardly noticed and cause but little heating at full s eed becomesat slow speed an enormous lea causing serious heating of atmospheres of vcompression and is well known and provided become superheated from no and often results in igniting the lubricating o1ls. Most of the .disastrous compressor explosions have been recorded as having occurred when the machines were running' slowly. It is therefore evident that when a compressor shows superheating, there is a certain degree of risk in attempting tostop the machine for the reason that no matter how quickly this may be accomplished, before it comes to a state of rest there must be some strokes of the pistons at aslow speed, and these strokes can do the damage.

The object of this invention therefore is to control the unloading ofa compressor by thermally actuated means and thereby when the temperature reaches a predetermined degree eliminate danger of accident and put the compressor in a safe condition to be stopped. To accomplish this I pro ose, when the air becomes superheated, to re ieve the pressure of the discharge until the temperature has become reduced to normal, and thus insure safety, and this is done in such a way as to remove all impediments to the proper valve actions, that is, to scavenge the cylinder of grease and gummy oils and clean the valves and the seats of foreign bodies which obstruct them and cause the leak, and contribute to the dangerous condition. This object is attained byJthe provision of means whereby whenever a compressor becomes superheated, a valve is opened so that the air will be exhausted directly from the cylinder to the atmosphere. This instantly relieves the pressure in the cylinder and stops the accretion of heat, and at the same time this opened valve allows a great out rush of air, vastly more rapid than the ordinary iiow through the machine even when running at its highest speed, -This air sweeping 'through the machine clears out all dirt and gumming oil from the cylinders, and from the faces of the valves and the valve seats cleans away all specks -or vforeign bodies. The opening of 'this relief valve is accomplished through the agency of electro-thermal means subjectedto the influence of the hot discharge air and, of course, when by reason of the relief and the cessation of iow in the discharge pipe of hot air, the thermometer ,again registers a lower temperature the reverse action takes place, allowing the relief valve to close and the machine to resume 'its work. -The blast of I 'granted August 15, 1911.

loaded, throttles the supply of air at the in take and at-the same time opens the discharge to the atmosphere so that no air will enter and all air will be pumped out allowing the pistons to move freely and relieve the engine of work. While the invention is'depicted in connection with a compressor provided with a valve that throttles the intake .at the same time that a discharge valve is openedto-the atmosphere, it is not essential to the invention that the intake be thus throttledriv v Figure 1: of the accompanying drawing shows thel essential parts of a three-stage compressor'of the type above mentioned provided with means which effect the object of this invention, valve, discharge cut in section to expose their interiors. Fig. 2 shows a modified arrangement for effecting the exhaust of air to the atmosphere when the temperature at the discharge end of the cylinder becomes abnormal.

The cylinders 1, 2 and 3 of the three-stage compressor illustrated have ordinary pistons 4, 5 and 6 connected in the usual manner. These cylinders are fitted with the necessary inlet and outlet valves, which are not shown as they are of common form and arrangementand are well understood. Air enters the low pressure cylinder 1 through the intake pipe 7 and is pumped by the piston 4 from that cylinder through the well known intercooler 8 to the intermediate cylinder '2. From this it is pumped by the piston 5 to the high'pressure cylinder 3, and from there, bythe piston 6, it is pumped through the outlet 9 to any suitab e reservoir 10. It is common to design such a compressor as that which is illustrated, so `as to raise'the air from 1 to 6 atmospheres in the low pressure cylinder, from 6 to 36 atmospheres in the intermediate cylinder, and from 36 to 216 atmospheres in the high pressure cylinder, or approximately 3160 pounds per square inch in the reservoir. In accomplishing this a large quantity of heat is generated, but under ordinaryv conditions this heatis taken care of by the design of the machine.

Connected withl the intake pipe shown is a the throttle valve, exhaust valve and controller being throttle valve 11. This is preferably of a balanced type so that it will work easily. In the interior this valvehas two disks 12, which are designed to close the ports under predetermined pressure conditions, and thus cut olf the supply of air to the cylinder 1. These valve disks are lifted for closing the ports by a p-iston vrod 13 that is pushed up when air is admit-ted into the cylinder 14,

below the piston 15. When there is no air pressure below the piston, this valve remains open. The air pipe 16 leads from the controller 17 to the cylinder 14 below the piston 15. The inlet to this cont-roller is connected by a pipe 18 with the reservoir. In this air controller is a valve 19 which isheld down to its seat by a spring 20. When the air pressure in the reservoir'rises sufliciently to overcome this springand` lift the valve 19, air Hows through the cont-roller and is exerted beneath the piston that acts to lift and close the throttle valve. In the head 21 at. the discharge end of the high pressure cylinder is a passage 22. .This passage is normally closed by a discharge valve 23 that is held to its seat by a spring 211. A pipe 25 connects this passage in the head,'beyond the discharge valve, with the interior of the exhaust valve casing 26. In the upper part of this casing is the exhaust valve 27 that is normally held closed by a spring 28. In A the lower part of the casing is a piston valve 29. Extending between these two valves is a stem 30. Opening from the interior to the atmosphere through the casing between these two valves is an outlet 31.

When the air controller is opened by the maximum pressure in the reservoir, the air passes into the lower part of the exhaust valve casing, and the pressure lifts the piston valve therein. valve, allowing such air as is forced past the discharge valve in the head of the high pressurecylindei" to iiow through the pipe 25 and through the exhaust valve casing to the atmosphere. When the compressor is working normally, the discharge valve 23 in the head will allow air to pass it and fill the pipe 25 as far as the exhaust valve to a degree equal to the reservoir pressure. Then the pressure being equal on both sides, the dischargevalve is held closed by its spring4 and becomes inoperative. When, however, the air pressure lifts the piston valve 29 and opens the exhaust, such air as is in the highv pressure cylinder is forced past the discharge valve by the forward stroke of the piston and exhausts to the atmosphere.

The thermal means is preferably a thermometer bulb 32 inserted into the discharge pipe 9 from 'the Ihigh pressure cylinder. This may be of the filled .with compressed' gas,vand it is connected by a exible tube 33 with a registering instrument 34 of well knownvdesignf common type which is causes the compressor `the temperature',

This instrument, while adapted to register is also constructed, as is commonly understood, so that when the temperature reaches a predetermined degree, an electric circuit is closed. In this circuit is the battery 35, and theremay be an electric bell 36 which will so-und an alarm when the maximum temperature. is reached and the circuit is closed. This style of registering thermometer and alarm is a Well `known commercial article, and a more extensive description is unnecessary. Connected with the stem 37 of the air controller valve 19 is the core 38 of a solenoid, the coils 39 of which are connected with the electric circuit that is opened and closed by the action of the thermal means. A compressorprovided with this apparatus unloads and works freely when a predetermined air pressure is reached. The thermal means also .to be immediately unloaded whenever the temperature of the air in the discharge reaches a predetermined degree. When this predetermined degree of temperature is reached, and through the thermometer the circuit is closed, the air -controller valve is lifted. When this valve is opened, with the apparatus above described, the air flows through the controller and lifts the exhaust valve so as to allow the air that is forced forward by the high pressure piston to pass the ,discharge valve and exhaust itself to the atmosphere. This affords instantaneous relief for the pressure and the rush of air that is permitted by the opening of the discharge and eX- haust valves scavenges the -cylinder and cleans the surfaces of the valves and'valve seats. v`When the air controller is open the' motion'but no air it escapes to the atcompressor continues in passes to the reservoir, mosphere, and

. jected to repeated compressions a large amount of heat is not generated. As the air escapes, the thermometer bulb will soon cool and the electric current will then .be

cut oit from the solenoid, allowing the controller to close so that the compressor will resume normal action and accomplish Work. Should the previous blast of air have been effectual in clearing all the valves, the machine Vwill continueto operate normally, but should heating again occury and a careful examination be desired, the compressor will automatically be placed in a safe condition 4to be slowed down and stopped .for the purose.

If desired, a controller valve may be connected directly with the discharge pipe, as shown in F ig. 2. i is arranged to close a passage 41 from a branch pipe 42 to thel atmosphere; The

opened by the pull of the solenoid, when the circuit is closed A and means designed to be as this air is not being sub- I'n this case the valve 40v by the action of abnormalr temperature on the thermal means, as previously described.

The invention claimed is :v

1. The combination with an air compressor cylinder having a piston, inlet and outlet valves, of means subject to the temperature at the outlet, an electric circuit adapted to be closed by said means when the temperature reaches a predetermined degree,

actuated by the closing ofy he electric circuit for .opening3 a discharge from the compressor cylinder.

2. The combination with an air compressor cylinder having piston, inlet and outlet valcves and unloading mechanism, of thermal means subject to the temperature o ,the air at the outlet and operatively connected with the unloading mechanism, said means when the temperaturei of the'air at the outlet reaches a predetermined degree, causing the unloading mechanism to be so actuated that the compressor eeases to compress `air.

3. The combination with an air compressor having a piston, inlet andl outlet valves, of means subject to the temperature at the outlet, an electric circuit adapted to be 4closed by said meanswhen the temperature reaches a predetermined degree, means designed to be actuated `by the closing of the electric circuit for opening a discharge to the atmosphere end of the cylinder, and an alarm adapted to be sounded by the closing of said circuit..

4. The combination with an air compressor cylinder having a piston, inlet and outlet valves and a discharge valve, of means subject to the action of thetempera- -ture at the outlet, an electric circuit adapted to be closed by said means when the temperature reaches a predetermined degree.. and an air controller adapted to be opened by the closing of said electric circuit, sai air controller being connected with the discharge valve, whereby when the controller is opened the cylinder will discharge air through said discharge valve.

5. The combination with anY air compressor cylinder having a piston, inlet valves, outlet valves and a discharge valve, of a thermometer arranged at the outlet and subject to the action'of the temperature, anH

electric circuit adapted to be closed by the -action of the thermometer when the temperature reaches a predetermined degree, an air controller designed to be opened lby the closing of said circuit, said discharge valve being connected with and relieved by the opening of the air controller so as .to permit air to be discharged from the cylinder to the atmosphere when the temperature reaches a predetermined degree.

6.' The combination with an pressor cylinder having a piston, outlet valves and a discharge valve,

air cominlet and of from. the high pressure the solenoid opens the air control and l.means subject to thc action of the tempera- .it `to be opened, whereby air will be dischargedfrom the compressor to the atmosphere through the discharge valve when the temperature reaches a predetermined degree. f

7. The combination with an air compressor cylinder having a piston,inlet and outlet valves and a discharge valve, of means subject to the action of the temperatureat the outlet, a circuit adapted to be closed by said means when the temperature at' the outlet reaches a predetermined degrec, a normally closed exhaust valve connected with the discharge valve, a normally closed air control connected with the eX- haust valve, and a solenoid connected with the electric circuit whereby when the circuit is closed by the action of the thermal means,

ermits the exhaust valve to move and relieve the discharge valve so that air will be forcedy past the discharge valve through the ex- I haust valve to the atmosphere as long as the temperature remains at the predetermined high degree.

8. An air compressor provided on the high pressure side with a discharge valve,

means subject to the temperature on the discharge side of the compressor, an electric circuit adapted to be closed by said means when the temperature reaches a predetermined degree, and means actuated by Said circuit for releasing the discharge valve and permitting it \to open.

9. The combination with an 4air compressor, of thermal apparatus subject to the EBENEZER HILL.

' Vitnesses: d

f E. HILL, J r.,

J. E. SLATER. 

